Auxiliary Digital to Analog Converter (DAC) is a very common functional block in the integrated circuit system. They are used in industrial control and automated test applications. They are needed for Automatic Gain Control (AGC) in communication transceivers ICs. For servo control system, a monotonic auxiliary DAC is crucial to close the servo loop. For data acquisition system, auxiliary DACs are widely used for the calibration or trimming of high-resolution data converters. For RF system, auxiliary DACs are employed to ensure I channel and Q channel gain matching and offset control. Auxiliary DACs are also an essential function in the high precision instrumentation system. The Micro-Controller Unit (MCU) and Field Programmable Gate Array (FPGA) all have the various auxiliary DAC feature for clients to exploit different functions. Auxiliary DACs are prevalent in nowadays integrated-circuit (IC) system.
As the systems get more complex and higher speed, auxiliary DACs with higher sampling rate and higher resolution are desired. The recent portable electronics are pushing for very low power auxiliary DAC. General purpose automated test equipment requires many channels of precisely controlled DAC outputs that span several voltage ranges. Large scale System-nn-Chip (SoC) integrated circuit employs many channels of auxiliary DACs to control the surrounding utility IC such as power management IC (PMIC) to deliver a precise voltage supply with respect to the environment change like temperature. Thus the occupied silicon area is also a great concern if the auxiliary DAC area is not compact enough.
A new architecture of single-ended capacitive DAC with transconductance (GM)-based buffer is developed to achieve features of high resolution, high sampling rate, wide supply range, extremely low power, compact area and also being able to drive high capacitive/low resistive load for auxiliary DACs.